Oscilloscope Buying questions

[jsi]

Guys I need a little help in purchasing a good oscilloscope and I am a little overwhelmed by all the choices, new, used, 50 MHz, 100 MHZ, etc, etc.  First this is what I need it for: My project “listens” to a telephone signal and depending on what it “hears” different actions are taken.  For example, if it hears DTMF tones different things happen than if it hears someone talking.  I’m getting strange results that I’m attributing to noise on the line, but I don’t really know for sure.  I’d like to plug in an oscilloscope and see what’s going on.  Beyond that I’d like to be able to use it at a logic probe to see what state different pins on the IC’s are in from moment to moment.

I think my needs are really simple, for now.  But, I can see more uses in the future so I want to buy a quality piece of kit that will last.  I’m a firm believer in crying once about the price of a tool than crying every time you use a cheap one.  That said my budget is $300 - $400 USD give or take.  Used is an option for sure.  Also my future uses could require the device to be portable so the new LCD screens are attractive.

There are a number of new oscilloscopes in my price range and more than quite a few on ebay.  Beyond a brand name what should I be looking for?  50, 100, 200 or more MHz? Other stuff?

[PartialDischarge]

You did pretty much say it all, if you want a portable LCD osc in that budget get a DS1054Z, or fish for something used on ebay...

That said, try to foresee your future projects and if you may be better off saving a few hundred more for a DS2000 for example, but hey a DS1054 will give you a lot to play with....
I dont even mention USB scopes... a waste of money....

[jsi]

One thing I don't understand is the different MHz.  The Rigol DS2072A is 70 MHz and about twice the price of the 100 MHZ Rigol DS1102E.  So clearly it's not all about the MHZ. 

As for the $400 budget lets uh, just say that's a guideline rather than a rule.  I'm at a stage in life where I can indulge a hobby.  And who knows, maybe this hobby can make me a few dollars to pay for the tools.

[nctnico]

What is pushing prices apart is bandwidth, samplerate, memory depth and maturity/functionality of the features. I think it is safe to say $400 doesn't buy you a new oscilloscope with features which all work as advertised or are actually useful. You really have to make a list with the features you want, look of oscilloscopes which provide those features and use reviews/comments on this forum to guage whether it is a good buy or not. This should get you a short list but be sure that you can return an oscilloscope if it turns out to be a lemon after all. The biggest mistake to make is to wait for a firmware update to fix a problem. If a feature isn't there 'out of the box' (after installing the most recent firmware) then return it ASAP.

[DimitriP]

My project “listens” to a telephone signal and depending on what it “hears” different actions are taken.

Potentially you can get away with any used , functional scope even if it has a single digit BW.
Even a cheapo Ebay $30 USB scope will allow you to look at "telephone line audio"
 

[rstofer]

It appears as though your experience with scopes might be a little thin.  If that's wrong, my apologies...

So, you can't make a list of features you need, you can't add in features you might want down the road, you're pretty much stuck at the starting point.

You mention a logic analyzer - that's not a scope!  An MSO scope can handle this kind of stuff but those tend to cost quite a bit more.

Most everybody is going to say "Get a DS1054Z 4 Channel scope, hack it to get to 100 MHz and it includes decoding for serial buses".  I haven't done that but I probably will and the procedure is well established.

Watch Dave's videos on the 1054 and see what he has to say.  For goodness sake STAY AWAY from the negative threads on this forum.  There are some truly vitriolic haters on those threads.  You will also see it in just about every thread that even mentions the word 'scope!

Rigol is pretty good bang for the buck at every level.  There are others such as Siglent and on up the food chain to Tektronix.  The cost just keeps climbing.

I bought a used Tektronix 465 scope about 12 years ago from eBay for a couple of hundred bucks.  They're still about that price...  It is rated for 350 MHz, only handles 2 channels and has no digital features at all.  It does, however, take care of any high frequency stuff I might want to do.  Realistically, the 1054 will handle most of my projects - actually all of them if I do the well-documented hack.

My advice (not that I expect anybody to pay attention to what I have to say), buy the DS1054Z, learn what digital scopes can or should do and, later on when needs change, buy something else and sell the 1054 if needed.  At least, the 1054 is a good place to start.  Right away it's got more channels than my 465 - that's why I bought it!

[jsi]

It appears as though your experience with scopes might be a little thin.  If that's wrong, my apologies...

You nailed it - no apologies needed

So, you can't make a list of features you need, you can't add in features you might want down the road, you're pretty much stuck at the starting point.

You mention a logic analyzer - that's not a scope!  An MSO scope can handle this kind of stuff but those tend to cost quite a bit more.

In the latest EEVblog #879 post Dave uses a scope to peer into the inner working of a chip (here's a link to where that starts in the video  https://youtu.be/3THvWEKGOwE?t=15m28s) and this is the sort of thing I want to do.  Is that pin high or low and when did it happen?  I noticed he is using an MSO scope.  But, confusingly for me, in this video https://youtu.be/MC9_4mpqVgU Dave says you can use the DS1054Z as a simple logic analyzer, and you can upgrade it to a true MSO scope if/when you need that functionality.

Most everybody is going to say "Get a DS1054Z 4 Channel scope, hack it to get to 100 MHz and it includes decoding for serial buses".  I haven't done that but I probably will and the procedure is well established.

Watch Dave's videos on the 1054 and see what he has to say.

I've watched that and it does look interesting

For goodness sake STAY AWAY from the negative threads on this forum.  There are some truly vitriolic haters on those threads.  You will also see it in just about every thread that even mentions the word 'scope!

Yeah isn't that true for every thing nowadays.  Fanboys are everywhere.

[billfernandez]

Given that presently you're only dealing with audio frequencies all you really need is 1MHz in scope bandwidth.

Scoping out logic will take more bandwidth depending on how fast it runs and what you want to see.

For this kind of basic tool I personally prefer to buy new, modern equipment rather than something used and/or something older and less current.

The Rigol DS1054Z is currently in the "best bang for the buck" sweet spot for a general-purpose, introductory-level scope.  I would think that this would last you many years, give you plenty of room and functionality to grow into, and depending on where you go with your hobby you might never have to upgrade.

And don't forget that if you make requests in the appropriate threads you can get discount codes for ordering through Tequipment.net and Saelig.

[bitseeker]

Since you're starting out with very modest requirements as far as the signals you're wanting to see (audio is pretty low bandwidth), almost any scope will work. Hence the comment that a 1 MHz scope will be plenty, including for looking at noise within the signal. The bandwidth rating indicates the highest frequency sine wave that can be measured before a given amount of attenuation occurs to the signal. More complex signals have higher frequency components that require more bandwidth to see correctly.

As has been mentioned already, for your budget you can get what you need and much more in the DS1054Z. Its 50 MHz bandwidth is many times more than what you currently need. If you outgrow it, you can sell it for something else (or keep it for projects where it fits), but that may be a while especially if you hack it to enable all the features, such as the protocol analysis, and 100 MHz bandwidth.

Later, if you want to analyze a lot of simultaneous digital signals, get a separate logic analyzer unless you really need to see the timing of analog signals concurrent with digital ones, which is where an MSO can be beneficial depending on how many you need to see at the same time. The four channels in the 1054Z can take you quite far.

[uncle_bob]

Hi

One of the modern facts of life is that all projects eventually go digital. That may not happen for a few years, but it does happen. When it does, a 1054 is a pretty good thing to have. Until then, it does what you need to do at lower frequencies just fine.

Bob

[Tomorokoshi]

Do those models have a basic FFT or spectrum analyzer view? With DTMF that would be a useful diagnostic feature.

[uncle_bob]

Do those models have a basic FFT or spectrum analyzer view? With DTMF that would be a useful diagnostic feature.

Hi

Yes, the 1054 has a basic FFT spectrum capability. It's not super duper, but it works. A sound card might do a better job for audio.

Bob

[rstofer]

Dave says you can use the DS1054Z as a simple logic analyzer, and you can upgrade it to a true MSO scope if/when you need that functionality.

I'm not sure how that could be done.  MSOs will have a separate port with the parallel inputs.  The DS1054Z with 4 channels will make a pretty decent analyzer for 3 channels + a clock or just 4 channels.

If you're going to be working at less than 1 MHz, the Hobby Components 8 channel logic analyzer seems pretty good.  I was testing it yesterday and I would be quite happy using it at sub-megahertz frequencies as long as I could sample at 24 MHz (USB 3.0 is probably required).

http://hobbycomponents.com/test/243-hobby-components-usb-8ch-24mhz-8-channel-logic-analyser

The software (open source) is pretty decent.  Just sample fast, don't take too many samples and keep the frequencies low.

There is no reason the scope has to perform as a logic analyzer and a LA certainly can't replace a scope.

I have a LA based on a project at www.sump.org.

[ez24]

You mention portable in the future.  They why think about a bench one ?  If you can spring for a little more take a look at this

http://www.amazon.com/Handheld-Portable-Oscilloscope-Multimeter-Hantek/dp/B00CTHC0O6/ref=sr_1_12?ie=UTF8&qid=1463200018&sr=8-12&keywords=hantek+oscilloscope

What ever you do buy one in the country you live in for the warranty.  For example if you live in the US and buy one from HK, you would have to mail it back to HK to fix.  Postage will cost a fortune.

[JPortici]

I dont even mention USB scopes... a waste of money....

In the low price range, of course. But hey, tell pico technology they just sell crap!

I agree with rstofer. Get the 1054z, go on with the hobby, learn it and learn to live with its many limitation and issues (still, the best you can get new in the low price area) and learn not to blindly trust your measurement tools
Then in the future when you'll get a scope that's not really better on paper but better in reality -less feature but that works as advertised, more responsive interface and so on.. i'll never buy a rigol scope again, the ds2k and ds4k have almost all the same hardware bugs.- you can still use it for less critical stuff for example, or sell it.

If you want to see the spectrum of signals in the audio frequency range any low tier usb audio interface will be eons better than any oscilloscope that hasn't got more than real 12 bits resolution, which rules out basically every scope in the "humane" price range, because a soundcard adc has got much more resolution and even if you throw away 4-5 bits for cheap adcs your true resolution will be higher so better noise floor.
If you need to accurately measure audio signals at dc to <10hz  you'll need a dc coupled audio interface, like MOTU's

[Fungus]

Dave says you can use the DS1054Z as a simple logic analyzer, and you can upgrade it to a true MSO scope if/when you need that functionality.

I'm not sure how that could be done.

It can't be done with a basic DS1054Z. You need to buy the model with the extra connector on the front (which is more expensive).

But yeah, the correct answer to "I have $400 and I want to buy an oscilloscope" is to get a DS1054Z. It's head and shoulders above anything else in that price range.

Four channels is enough for simple logic analysis work.

There are a number of new oscilloscopes in my price range

But only one worth having.

Beyond a brand name what should I be looking for?  50, 100, 200 or more MHz? Other stuff?

More MHz is always good. More channels is always good for logic work.

A new $400 'scope with more MHz and channels than a DS1054Z? Impossible.

[Wuerstchenhund]

Most everybody is going to say "Get a DS1054Z 4 Channel scope, hack it to get to 100 MHz and it includes decoding for serial buses".  I haven't done that but I probably will and the procedure is well established.

Watch Dave's videos on the 1054 and see what he has to say.  For goodness sake STAY AWAY from the negative threads on this forum.  There are some truly vitriolic haters on those threads.  You will also see it in just about every thread that even mentions the word 'scope!

Well, to be fair there's some basis to the critics of Rigol:
https://www.eevblog.com/forum/projects/project-yaigol-fixing-rigol-scope-design-problems/

That doesn't render the scope useless, but it is a pretty stark display of incompetence in terms of designing hardware properly, and a prospective buyer should be at least aware of the problem and what's required to fix it.

Rigol is pretty good bang for the buck at every level.

No, certainly not at every level. Rigol offers without doubt the best value for money at the bottom end (DS1054z), and the DS2000A has been similar value for money back then when it was only competing with the Agilent DSOX (but these days there are more alternatives), but the DS4000 in general isn't (again, there are other alternatives these days), and the DS6000 is pretty much a bad joke with a ridiculous price tag.

There are others such as Siglent and on up the food chain to Tektronix.  The cost just keeps climbing.

Yes, but Siglent, while producing good hardware, has a long and very poor track record with their firmware quality. It doesn't mean the scope won't do what the OP wants it to do, but it's important to be aware of the limitations and issues, and as nctnico says, if it doesn't work today don't get fooled into waiting for a fix, return it.

It also shows that in general you get what you pay for, although Tek (the once great brand that gave us the best analog scopes but since the advent of DSOs has only come up with mostly mediocre at best products, and today it pretty much represents the bottom-end of the big brands) shows that this isn't always true.

My advice (not that I expect anybody to pay attention to what I have to say), buy the DS1054Z, learn what digital scopes can or should do and, later on when needs change, buy something else and sell the 1054 if needed.

I fully agree. At a budget of $400 the DS1054z offers the most bang for the buck. The 2nd hand market often has great deals but at $400 there's pretty much only "untested" (i.e. known defective) digital stuff, some old sampling scopes (useless for everything except some niche tasks) and some analog antiques (which realistically shouldn't cost more than $50 or so). So yes, the DS1054z is the best option here.

[EEVblog]

In the latest EEVblog #879 post Dave uses a scope to peer into the inner working of a chip (here's a link to where that starts in the video and this is the sort of thing I want to do.  Is that pin high or low and when did it happen?  I noticed he is using an MSO scope. 

I did not use the MSO function of that scope Keysight scope!
I used the analog channels, because I like to look at the actual waveforms.
Just get the Rigol DS1054Z, it will do everything you want

[DimitriP]

...in the meantime , while you are deciding how to spend $400 to deal with DTM tones,

download this  http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=18988  ,  feed the sound to your soundcard and get some work done

[PartialDischarge]

I dont even mention USB scopes... a waste of money....

In the low price range, of course. But hey, tell pico technology they just sell crap

I said they are a waste of money, I dont care if its 10MHz or 2Ghz bandwidth. A scope is a scope and a laptop/PC running Windows plus an usb box is crap ( and a waste of money) no matter how good the specs.

Same applies for example to hikers/mountaineers saying "hey my phone has a gps, so Ill use that one during the hike" A phone is a phone( low battery life, useful for emergency calls, no waterproof...) and a Hiking gps is a GPS.

[JPortici]

I disagree. It's not that there are plenty of scopes that are
-battery powered
-with isolated channels
-with good analog front ends
That also are not crippled or limited in the software side.

[Fungus]

Well, to be fair there's some basis to the critics of Rigol:
https://www.eevblog.com/forum/projects/project-yaigol-fixing-rigol-scope-design-problems/

That doesn't render the scope useless, but it is a pretty stark display of incompetence in terms of designing hardware properly, and a prospective buyer should be at least aware of the problem and what's required to fix it.

Has anybody demonstrated that any of those design defects has an effect on the 'scopes output?

Because if they don't, then...who cares? 

[alsetalokin4017]

In the latest EEVblog #879 post Dave uses a scope to peer into the inner working of a chip (here's a link to where that starts in the video and this is the sort of thing I want to do.  Is that pin high or low and when did it happen?  I noticed he is using an MSO scope. 

I did not use the MSO function of that scope Keysight scope!
I used the analog channels, because I like to look at the actual waveforms.
Just get the Rigol DS1054Z, it will do everything you want

Right!

After all, what other scope can display 5 bugs at once?

(Don't get me wrong, I ordered the scope based on Dave's reviews, and overall am very happy with it, and with RigolUSA's customer service. But.... there are some bugs that some people might find critical...)

[MT]

List the 5 bugs! Hmm.. are there a 6'th bug?!

[jsi]

...in the meantime , while you are deciding how to spend $400 to deal with DTM tones,

  not quite up to $400 for the DTMF tones.  I salvaged a MT8870 DTMF processor out of an old call processing box. And thank you for the link, you never know when stuff like that will prove useful.  Eventually this project is going to go into a project box and be used daily, but I'm a long ways from that right now. 

And a big thanks to everyone that chimed in, my next post will on the TEquipment thread to request a discount for the Rigol DS1054Z. It's in my price range, small and portable for my other uses, it's new with a warranty so I don't have to worry about getting a bad used one, sexy looking, and after everyone's input I'm sure it will do what I need. 


(to my dear sweet wife I'm going to say "your brother just spent $500 on a single golf club and he's still a lousy golfer, so really my hobby isn't that expensive"  )